The development of terahertz graphene electronics requires a variety of fundamental questions to be addressed. This project will use epitaxial graphene on SiC as an unprecedented platform to answer these questions. The work is broken into three parts. In the first set of experiments, the very first studies of growth kinetics in a high-pressure furnace environment using x-ray scattering will be carried out and lead to a better understanding of graphene growth. In the second part of the research, the patternabilty of epitaxial graphene will be exploited to grow large area arrays of graphene nano-ribbons. These arrays will allow, for the first time, photoemission studies of the width dependent gap. Finally, the ribbon arrays will allow various adsorbents to be side diffused into the graphene-SiC interface. This work will allow controlled experiments on compensation doping of graphene ribbons to overcome charge transfer from the SiC. Graduate and undergraduate students will not only learn a variety of highly specialized experimental techniques, but they will also have the opportunity to become forefront researchers in graphene electronics development.
The competitive advantage of the US electronics industry requires a solution for the approaching end of silicon-based electronics. Epitaxial graphene offers a serious promise to drastically surpass silicon and lead to ultra high-speed electronics. While epitaxial graphene is a radical electronics material, it requires novel device designs, growth methods and materials challenges to be understood and tested before graphene enters commercial or military systems. The research carried out under this program addresses these challenges. The very first studies to understand graphene growth in a high-pressure furnace environment will be carried out. Research will involve new techniques to produce ultra thin graphene ribbons that will allow studies of this new material's unique electronic properties. Graduate and undergraduate students participating in this research will not only learn a variety of highly specialized experimental techniques, but they will also have the opportunity to become forefront researchers in graphene electronics development. This highly trained workforce will allow the US to continue its lead in the Global electronics industry.
Graphene is a unique form of carbon whose singular properties were first recognized in 2001 as a potential replacement for silicon in next generation electronics. While research in this new material exploded since 2003, the lack of a way to make a semiconducting form of graphene has stymied its incorporation into mainstream electronics. Under this grant, we have shown that graphene ribbons become semiconductors as they flow and bend over artificially produced step edges cut into silicon carbide. These ribbons are referred to as "sidewall" graphene ribbons. We have developed the techniques to produce these same ribbons on a technologically relevant scale. Using standard patterning technology and high-resolution microscopy coupled with state of the art two-dimensional analytical tools, we have shown that large-scale sidewall ribbon graphene can be made with uniform structural and electronic properties. An example image is shown in Figure A Because the electronic properties of graphene ribbons depend on the geometry of their edges, it is critical to know how to grow ribbons with different edges. For graphene there are only two important edges that we refer to a Armchair (AC) and Zig-Zag (ZZ). We have shown that sidewall graphene ribbons grow very differently depending on the step direction. AC ribbons actually grow in very small parallel ribbons and the risers of the steps as shown in Figure B. These very small ribbons are the first example of a two dimensional semiconducting form of graphene. ZZ edge graphene grows very differently. The ZZ ribbons grow in a narrow stripe at the top of the edge as shown in the comparison growth model in Figures C and D. These ribbons are metallic. What we have shown under the work in this grant is that we can grow both metallic and semiconducting graphene ribbons simply by switching which directions we pattern step edges in SiC. This opens up new and exciting possibilities for graphene electronics. The advances in graphene modification produced under this research program will play an important part in accelerating the development of carbon electronics. Because carbon based materials can operate at higher temperatures, in corrosive environments, and use less power, carbon electronics offers a significant advancement for the US electronics industry. This research represents an important step forward in the development of next generation electronics.
